Fiber application machines, commonly referred to as fiber placement machines, are known for the application on a draping tool, such as a male or female mold, of a wide strip formed of several ribbon-type dry or resin impregnated flat fibers, in particular carbon fibers, comprised of a multitude of carbon threads or filaments, dry or impregnated with a thermosetting or thermoplastic resin.
Fiber application machines are used to produce preforms formed from several superposed plies, with each ply formed by draping on the mold of one or several joining strips. In the case of a draping of fibers pre-impregnated with resin, the preform, referred to as preimpregnated, is hardened or polymerized by passing through an oven to obtain a composite material part. In the case of so-called dry fibers, fiber that are not preimpregnated with resins, but possibly comprising a very reduced quantity of resin, referred to as a binder resin, to confer a sticky nature to the fibers during the draping, resin is injected or infused into the dry preform before the step of hardening.
These machines, such as described in patent document WO2006/092514, conventionally include a fiber application head, a system for displacing said fiber application head, fiber storing means, and fiber conveying means to convey the fibers from said fiber storing means to the application head.
The fiber application head, also called fiber placement head, conventionally comprises an application roller intended to come into contact against the mold to apply the strip, and means for guiding fibers onto said application roller. The head generally further comprises a heating system to heat the fibers. The compaction roller presses the strip of fibers against the application surface of the mold, or against the strip or strips of fibers previously deposited, in order to facilitate the adherence of the deposited strips between them, as well as to progressively remove the air imprisoned between the deposited strips. The heating system provides heating of the strip of fibers, and/or of the mold or of the strips already applied upstream of the compaction roller, just before the compaction of the strip, in order to at least soften the pre-impregnation resin or the binder resin, and as such favor the strips adhering together.
The displacing system provides for the displacement of the application head according to at least three directions perpendicular to one another. The displacing system may be formed by a standard six-axis robot type poly-articulated arm, arranged on the ground or mounted on a linear axis, with an end wrist to which the application head is fixed, or by a gantry-type Cartesian-coordinate robot provided with an end wrist carrying the application head.
In the case of fibers packaged in the form of spools, the fiber storing means conventionally comprise a creel or spool cabinet. The creel can be arranged on the ground in the vicinity of the application head, for example in the case of a fixed standard robot, or can be mounted on a member of the displacing system, for example on one of the carriages of the Cartesian-coordinate robot or on a follower-carriage sliding on the linear axis of the standard robot.
Such as described in the aforementioned patent document, the conveying means are advantageously formed of flexible tubes connecting the storing means to the application head, each flexible tube being able to receive a fiber in its internal passage. The flexible tubes can be placed in a sheath, such as described in patent document WO2010/049424.
For the safety of the operators, the machine is placed in a so-called safety zone, defined by a safety system, for example a perimeter safety system, such as a wire mesh lateral barrier surrounding the machine, in such a way that an operator cannot be present in the safety zone during the automatic operation of the machine, in particular during the automatic displacement of the head by the displacing system.
The operator cannot access the machine, in particular the head and/or the creel, without stopping the machine to carry out maintenance and/or verification operations, or without switching to a manual mode with limited speed. These interruptions substantially increase the production time of the parts, and therefore the effectiveness of the machine. In the case of a large-size machine, the access time to the machine for the operator can be substantial. Moreover, the safety system must have a dimension that is sufficiently large to integrate the entire machine, and represents a substantial cost.
What is needed is a machine that overcomes the aforementioned disadvantages, that is effective while still guaranteeing good safety conditions for the operators.